Fertilizer and process of making same.



995,028. No Drawing. I

UNITED STATES PATENT OFFICE.

srnncnn n. nnwnnanx AND HARVEY N; namr'r, or surnames, onro.

rnn'rrmzna AND 'rnocnss or MAKING shun.

To all whom it may-concern.-

Be it known that we, SPENCER B. New- BERRY and HARVEY N. BARRETT, citizens of the United States, residing at Baybridge,

in the county of Erie and State of Ohio,

have invented a certain new and useful Improvement 1n Fertilizers and Processes of Making the Same, of which the following is a specification.

Our invention relates to a process by which. natural phosphate of lime or phosphate of iron or-alumina, known as phosphate rock, or other mineral or animal phosphates in which the phosphoric acid contained is in an insoluble form, maybe simply and cheaply converted into a condition in which substantially all the phosphoric acid contained is soluble in ammonium citrate solution, and readily assimilable vfromthe soil in the process of plant growth.

It is well known that the processby which phosphate rock is ordinarily made soluble 15 by treatment at ordinary temperatures several well-recognized drawbacks, among which may be mentioned the large amount" with sulfuric acid in 'suflicient amount to convert the insoluble tricalcium phosphate of the rock into water-soluble mono-calcium phosphate or .so-called superphosphate, ac-

cording to the equation,-

acid are required for each equivalent of tricalcium phosphate. This process presents of sulfuric acid required, the difficulty of drying the product for convenientshipment,

the :inapplicability'of the process to phosphates containing more than a very smallpercentageof alumina and iron'oxid, the tendency of the superphosphate'to become again insoluble on storage, and the injurious effect on certain soils of the large amount ofsulfate of lime contained in the product. Our experiments-have shownthat all these drawbacksk -rnaybe overcome, and a product obtained icontaining practically no sulfate, in-vwhich substantiall all; the phosphoric acid is in citrate solu is form,

by a process consisting of -th.e' following steps: 1. Grinding the phosphate to fine powder. 2. Mixing the ground phosphate with an amount-of sulfuric acid correspond Specification of Letters 1mm. P t nt June 13, 1911, Application filed September 30, 1910. Serial No. 584,627.

' ing approximately to one equivalent of acid to each equivalent of .tri-calcium phosphate. 4 3. Drying and calcining ground phosphate and acld, in an oxidizing atmosphere, at a temperature suflicient to Oa (PO CaH, (P0 QOaSO,

In this operation, which takes place on mixingthe acid and ground phosphate, approximately one-half the "phosphate is converted to water-soluble acidcalcium phosphate, the other half of the raw phosphate remaining unchanged.

Reactions 2, 3, and 4: take place in the ca-lcination of the mixed phosphate and acid. In this operation the acidcalcium phosphate reacts with the unchanged tri-calcium phosphate to form di-calcium phosphate,

the heat of calcinationto form calcium pythe mixture of more or less completely decompose the cal .clum sulfate formed, with liberation of sul- CaHPO which is further decomposed by rophosphate, Ca P O. with evolution of water. .7 The calcium sulfate formed in reaction one 'is also, to a large extent, decomposed to lime, with evolution of sulfur dioxid and oxygen. The. product of the operation is thereforeessentially a mixture or compound of calcium pyro-phosphate and free lime. Prepared as above described it is a dry powder, containing a percentage of citrate-soluble phosphoric acid somewhat higher than that of the total phosphoric acid in the rock treated, and free from tendency'to change on storage. It is superior to 'superphosphate on account of its permanence, practical freedom from sulfates, much higher proportion of' soluble phosphoric acid,"and greater'fer'tilizing value owing to its more gradual solubility."

"As a practical example of the working of our process, we take phosphate rock or mineral phosphate, grind it'to fine powder, and mix it, in a suitable-vat preferably provided with mechanical stirring apparatus, with an amount of sulfuric acid corresponding ap- I tion ofacid above stated, as a considerably greater or less amount may be employed contained int-he roc proximately to 98 parts pure H S O to .319

parts tri-calcium hos hate, Ca,(PO,) t is economical to use the acid in the form of chamber acid, containing about 60 per cent. pure H,SO,. If the raw rock contains carbonate of lime,

an additional amount-of acid, about e ual'in weight of ILSO to the weight of car on'ate present, is used. We do not intend to confine our' invention .to the use of the propora calcining furnace andsubjected to bright orange ox dizing heat, of 2500 degrees to 2800 degrees F., until volatile matters cease to be liberated and the calcined material is brought to a sintered or semi-fused condition. The furnacelmay be of any suitable type, but best and most economical results are obtained by the use of revolving cylindrical kilns similar'in construction and operation to the kilns used in calcining Port-- land cement.--

r The acidgases liberated in the calcinat-ion may, if objectionable, be condensed by the usual methods.

- The calcined product, after cooling, is

ground to fine powder and is then ready to be used as fertilizer or as an ingredient of commercial fertilizers. 'Weclaim:

1. The process of making fertilizer by mixing natural phosphate withsulfuricacid and calcining the mixture at high temperature until sulfates are substantiall decomposed with liberation of sulfur ioxidand oxygen.

. product;

2. The process converting insoluble phosphates into citrate-soluble form by treating the phosphates with'sulfuric acid and calciningthe mixture at high-temperature until sulfates are substantially decomposed with liberation offisulfur dioxid and oxygen;

3.' The process of making fertilizer by grinding natural phosphate, mixing with sulfuric acid, and calcinin the mixture at high temperature in an oxi izing atmosphere until sulfatesare substantially decomposed with liberation of sulfur dioxid and oxygen. 4. The process" of making fertilizer by grinding natural phosphate, mixing with an amount of sulfuric =acid corresponding approximately to one equivalent of. sulfuric acid to each equivalent of phosphoric acid, P 0 contained in the phosphate, calcining the mixture at high temperature until sulfates are substantially decomposed with I liberations of sulfur dioxid and oxygen, and grinding the calcined product a j 5. The process of making fertilizer by grinding natural hosphate'," mixing with an amount of sul uric acid corresponding approximately to onevequivalent of sulfuric acid to each'equivalent of phosphoric acid, 7

13.0 containedin the phosphate, calcining in an oxidizing atmosphere at a temperature sufiiciently high to more or less completely decompose the calcium sulfate formed in the mixture, and grinding the calcined 6. Afertiliz' mammm'consisting essen-. tially of limean calcium pyro-phosph'ate in calcined condition.

7. A fertilizing material consisting essentially of lime and calcium pyro-phosphate in calcined condition, substantially free from sulfates;

' SPENGERB. NEWBERRY.; HARVEY N-.'BARRETT-. Witnessesr a 'WmJAu L..Taosr,

ALLEN Korma. 

